1. Field of the Invention
The present invention relates to an optical waveguide for propagating light in cores, to an optical waveguide device composed of an optical waveguide to which added are optical fiber guides for mounting optical fibers, optical components such as light emitting devices, light receiving devices, and the like, and functional portions such as optical device installing portions and optical modulation functions, and to a method of manufacturing the optical waveguide and the optical waveguide device, as well as to an optical communication apparatus using the optical waveguide device.
2. Description of the Background Art
Optical fiber cables used in optical communication employ an optical waveguide device at connecting portions and terminal ends so that the optical fiber cables can be connected to other optical fiber cables, light emitting devices, and light receiving devices. In recent years, as optical communications, which can transmit a large amount of data at a high speed, are increasingly used, it is desired to manufacture optical waveguide devices suitable for mass production at low cost.
There are optical transceivers as an example of an optical waveguide device for receiving an optical signal from an optical fiber and converting it into an electric signal and for converting an electric signal into an optical signal and transmitting the optical signal to an optical fiber. The optical transceiver is ordinarily composed of an optical waveguide substrate, on which an optical waveguide is formed, optical fibers connected to the cores of the optical waveguide, and a support substrate on which light emitting devices, light receiving devices, and the like are mounted. A filter insertion groove is formed midway of a core on the optical waveguide substrate so as to divide the core, and a filter, which has such characteristics that light having a particular wavelength range can be passed therein and light having other wavelength range is reflected thereby, is inserted into the filter insertion groove. A transmitting signal is separated from a received signal by the filter, and thereby, occurrence of crosstalk is prevented.
Conventionally, the optical waveguide devices are manufactured by individually manufacturing the optical waveguide substrates and the support substrates and bonding them to each other by a bonding agent one by one. Thus, a manufacturing process is complex and a long time and high cost are required to manufacture the optical waveguide devices. As a result, it is impossible to effectively manufacture the optical waveguide devices. Further, since the respective optical waveguide substrates and support substrates are minute components, it takes a long time and is expensive to assemble an optical waveguide device by aligning an optical waveguide substrate with a support substrate with a pinpoint accuracy.
Incidentally, productivity of the optical waveguide devices may be improved if they are manufactured in such a manner that a plurality of optical waveguide substrates and a plurality of support substrates are formed on wafers or mother substrates respectively at a predetermined interval, and after both the wafers or the mother substrates are joined to each other, the joined member is cut off to the respective optical waveguide devices. The production efficiency of the filter insertion grooves may be also improved by forming them at a time before the respective optical waveguide devices are cut off.
FIG. 1 shows a state in which a plurality of optical waveguide devices are formed. Optical waveguide devices 23 shown in FIG. 1 are composed of a plurality of support substrates 25, which are formed on a single mother substrate in a matrix, joined to a plurality of optical waveguide substrates 24 formed on another single mother substrate in the matrix. Although the optical waveguide substrates 24 are illustrated as if they are joined to the support substrates 25 in a discrete state, this is because unnecessary portions are not illustrated, and they are not cut off individually. Each optical waveguide substrate 24 has a core 26 that is cut off by a filter insertion groove 27. The filter insertion groove 27 is formed in the vicinity of the coupling portion of the core 26 formed in a T-shape, and a filter 28 is inserted in the filter insertion groove 27 so as to divide the core 26. The filter 28 separates a transmitting signal propagated in the core 26 from a received signal propagated therein.
The filter insertion groove 27 is formed in manner of making a cut by dicing. However, the dicing can only form grooves all over the mother substrate as shown in FIG. 1 and cannot form partial grooves only at portions where the filters 28 are inserted. Further, each filter insertion groove 27 is formed at a predetermined angle to the longitudinal direction of a core 26. Thus, if the filter insertion grooves 27 at predetermined positions of the respective optical wave guide devices 23 are formed, dicing pitches may not be set constant or positions 29 other than the targets positions of the cores 26 of other optical waveguide devices 23 disposed side by side may be divided depending upon the size of the respective optical waveguide devices 23 and the length of the cores 26. Accordingly, the respective optical waveguide devices 23 cannot be manufactured in the same shape.
An object of the present invention is to provide a method for manufacturing an optical waveguide device, in which respective optical waveguide devices can be obtained in the same shape from a substrate or the like and filter insertion grooves formed thereto do not cross undesired portions of the cores of other optical waveguide devices.
Note that although the filter insertion grooves 27 are illustrated in a width smaller than that of the filters 28 in FIG. 1 for the sake of convenience, actually, the width of the filter insertion grooves 27 are larger than that of the filters 28, and the filters 28 are inserted therein. Further, it is observed as if the filter insertion grooves 27 are formed also on the support substrates 25 other than the optical waveguide substrates 24, the portions of grooves 27 on the support substrates 25 show traces of a dicing blade. Since it is sufficient to form the filter insertion grooves 27 in a depth by which the cores 26 of the optical waveguide substrates 24 are completely divided, actually, the filter insertion grooves 27 are not formed up to the support substrates 25.
In a method of manufacturing an optical waveguide device according to a first aspect of the invention, comprising the steps of forming a plurality of optical waveguides, each of which comprises cores each having at least one branch point and passing and propagating light and clads surrounding the cores, on a first substrate in matrix at predetermined intervals longitudinally and laterally, forming a plurality of functional portions on a second substrate in matrix at predetermined intervals longitudinally and laterally similarly to the optical waveguides, bonding the first substrate to the second substrate and integrating them such that the optical waveguides face the functional portions, forming grooves, into which filters for passing or reflecting light having passed through or propagated in the cores according to the wavelength thereof can be inserted, at least at positions where the light reflected by a filter inserted into a groove at a branch point is propagated to a core extending in a different direction from the branch point, and thereafter cutting off the first and second substrates having been integrated to respective chips to thereby manufacture the optical waveguide device, the method further comprises the step of determining the disposing distances of the respective optical waveguide devices disposed in matrix, the lengths of the cores, and the forming distance of the filter insertion grooves so that the following relationships are satisfied.
x=mxc2x7p/sin xcex8 (m=natural number of at least n)
y=p/cos xcex8
zxe2x89xa6(n+1)xc2x7p/sin xcex8
where the distance in a longitudinal direction of the disposing distances is shown by x, the distance in a lateral direction thereof is shown by y, the length of the cores formed in a direction parallel with the longitudinal direction is shown by z, the number of the branch points of each core is shown by n, the forming distance of the filter insertion grooves is shown by p, and the inclination of the filters with respect to the longitudinal direction is shown by xcex8 (0xc2x0 less than xcex8 90xc2x0)
In a method of manufacturing an optical waveguide according to a second aspect of the invention comprising the steps of forming a plurality of optical waveguides, each of which comprises cores each having at least one branch point and passing and propagating light and clads surrounding the cores, on a first substrate in matrix at predetermined intervals longitudinally and laterally, forming grooves, into which filters for passing or reflecting light having passed through or propagated in the cores according to the wavelength thereof can be inserted, at least at positions where the light reflected by a filter inserted into a groove at a branch point is propagated to a core extending in a different direction from the branch point, and thereafter cutting off the first substrate to respective chips to thereby manufacture the optical waveguide device, the method further comprises the step of determining the disposing distances of the respective optical waveguide devices disposed in matrix, and the forming distance of the filter insertion grooves so that the following relationships are satisfied.
x=nxc2x7p/sin xcex8
y=p/cos xcex8
where the distance in a longitudinal direction of the disposing distances is shown by x, the distance in a lateral direction thereof is shown by y, the number of the branch points of each core is shown by n, the forming distance of the filter insertion grooves is shown by p, and the inclination of the filters with respect to the longitudinal direction is shown by xcex8 (0xc2x0 less than xcex8 less than 90xc2x0)
According to the method of manufacturing the optical waveguide device of the first aspect of the invention, when the filter insertion grooves are formed by dicing in the state in which the plurality of optical waveguide devices are formed on the first substrate, the functional portions are formed on the second substrate, and the first substrate is bonded to the second substrate, the respective optical waveguide devices can be formed in the same shape, and the filter insertion grooves formed to the respective optical waveguide devices are not divided at portions other than the target portions of the cores. Further, since the filter insertion grooves can be formed by setting a dicing pitch constant, the plurality of filter insertion grooves can be formed by automatically moving a dicing blade in the same process. Accordingly, it is not necessary to form the filter insertion groove to each of the optical waveguide device in a separate process, thereby the manufacturing process of the optical waveguide device can be greatly simplified and a manufacturing efficiency can be enhanced.
The manufacturing method of the optical waveguide according to the second aspect of the invention can achieve an effect similar to that of the effect of the first aspect of the invention except that the second substrate is not provided by the manufacturing method of the second aspect.
An inexpensive optical waveguide device having stable quality can be manufactured by the manufacturing method of the optical waveguide device according to the first aspect of the invention.
Further, there can be obtained an optical communication apparatus for converting an optical signal into an electric signal which comprises the optical waveguide device according to a modification of the third aspect of the invention, a light emitting device drive circuit for driving a light emitting device mounted on the optical waveguide device, and a data processing circuit for processing an electric signal output from a light receiving device mounted on the optical waveguide device.